Vascular territory segmentation using mutual clustering information from image space and label space

ABSTRACT

Methods, systems, computer programs, circuits and workstations are configured to generate at least one two-dimensional weighted CBF territory map of color-coded source artery locations using an automated vascular segmentation process to identify source locations using mutual connectivity in both image and label space.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/775,271, filed Sep. 11, 2015, which is a § 371 national phaseapplication of PCT/US2014/020552, filed Mar. 5, 2014, which claims thebenefit of and priority to U.S. Provisional Application Ser. No.61/788,826, filed Mar. 15, 2013, the contents of which are herebyincorporated by reference as if recited in full herein.

BACKGROUND

Carotid or vertebrobasilar stenosis restricts distal blood flow, whichdecreases blood supply to the parts of the brain subserved by thesevessels, and increases the risk of ischemic stroke. Surgicalintervention with carotid endarterectomy or endovascularangioplasty/stenting is generally pursued if the diameter of the lumenof the internal carotid artery (ICA) is reduced more than 70%, which istypically documented by noninvasive imaging. Collateral circulationincreases in the brain as a normal physiologic mechanism to by-pass andcompensate for the blockage in the main artery. In some cases, thisincreased collateral flow can supply enough oxygenated blood to maintainadequate cerebral perfusion for supporting brain function in symptomfree patients. The importance of adequate hemodynamic compensation viacollateral circulation has been shown in patients with cerebral arterialstenosis.

Focal arterial stenosis can be clinically evaluated using a variety ofimaging methods, including duplex ultrasound, computed tomographyangiogram (CTA), and magnetic resonance angiography (MRA). Althoughinvasive CT-based methods have been used for qualitative assessment ofvascular territory perfusion, quantitative mapping of blood flow fromindividual source arteries is still not practical in the clinicalsetting. Vascular territory mapping using arterial spin labeling (ASL)has been proposed, but currently typically requires complicated planningprior to scanning and extensive post-processing, which hinders thepractical clinical use of these methods. Psuedo-continuous ASL (PCASL)tagging can be used for vessel-encoded ASL (VE-ASL) utilizing gradientsapplied during the tagging period to spatially encode multiple feedingarteries. See, e.g., Wong, MRM, 58: 1086-1091, 2007; ISMRIM; 581, 2012;and Wong and Guo, MAGMA 25: 95-101, 2012. Strategies has been devisedfor the detection of source arteries without a priori knowledge ofvessel locations using a random encoding scheme (see, Wong & Guo, 19thISMRM: 294, 2011) or a Fourier encoding scheme (see, Jung, 20^(th)ISMRM: 581, 2012). The source artery location at the labeling plane isestimated on a voxel-wise basis in the image volume but a territoryoften needs to be manually identified. The source location of aterritory is often wide-spread due to noise and large vessel diameters,becoming more complicated when the labeling plane includes a largenumber of source arteries.

There is a need for clinically acceptable methods for visualization andquantification of perfusion territories from major feeding arteries inthe brain.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention are directed to methods, systems andcircuits that can automatically segment an image volume into separatevascular territories using mutual clustering in image and label space.

Embodiments of the invention provide systems, methods, circuits,workstations and methods suitable for automated vascular territorymapping for resolving source locations and to determine if multiplesources in different perfusion territories are from a single artery.

Embodiments of the invention may be particularly useful for MRI brainscans for evaluation of large artery diseases, cerebral vasculardisease, and carotid stenosis and may also be useful for stroke,especially thromboembolic stroke, and/or for evaluation of treatments orclinical trials.

Embodiments of the invention may be implemented as a routine brain scanfor neurological evaluations due to the automated processing and shortMRI signal acquisition time required for vascular mapping that can beprovided in a color map that represents both location of source arteries(typically by a predefined different color for each artery and/orlocation direction) and amount of perfusion (typically in brightnessand/or opacity).

Some embodiments are directed to methods of color mapping brain vascularperfusion using MRI. The color map can indicate the associated feedingartery per voxel in unique colors. For example, right internal carotidartery may be depicted in blue, left internal carotid artery in red, andright vertebral artery in cyan, and left vertebral artery in yellow.

The methods can include displaying the at least one map on a clinicianworkstation.

The segmentation analysis can be carried out using a processorassociated with an MR Scanner and/or at least one clinician workstation.

Some embodiments are directed to image and/or data processing circuitsconfigured to carry out any of the above steps or features.

It is noted that aspects of the invention described with respect to oneembodiment, may be incorporated in a different embodiment although notspecifically described relative thereto. That is, all embodiments and/orfeatures of any embodiment can be combined in any way and/orcombination. Further, any feature or sub-feature claimed with respect toone claim may be included in another future claim without reservationand such shall be deemed supported in the claims as filed. Thus, forexample, any feature claimed with respect to a method claim can bealternatively claimed as part of a system, circuit, computer readableprogram code or workstation. Applicant reserves the right to change anyoriginally filed claim or file any new claim accordingly, including theright to be able to amend any originally filed claim to depend fromand/or incorporate any feature of any other claim although notoriginally claimed in that manner. These and other objects and/oraspects of the present invention are explained in detail in thespecification set forth below.

The foregoing and other objects and aspects of the present invention areexplained in detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a schematic illustration of a sequence of exemplary automatedvascular segmentation steps for vascular territory mapping according toembodiments of the present invention.

FIG. 2A is an image with exemplary label plane locations according toembodiments of the present invention.

FIG. 2B shows the estimated source locations overlaid on maximumintensity projection (MIP) of the upper label location of FIG. 2A.

FIGS. 2C shows corresponding CBF weighted territory maps for FIG. 2B.

FIG. 2D is an image with estimated source locations overlaid on MIP ofthe lower label location of FIG. 2A.

FIGS. 2E shows corresponding CBF weighted territory maps for FIG. 2D.

FIG. 3 is a flow chart of operations that can be used for vascularterritory mapping according to embodiments of the present invention.

FIGS. 4A-4C are schematic illustrations of systems and circuits that canbe configured to provide the Fourier encoded ASL according toembodiments of the present invention.

FIG. 5 is a block diagram of a data processing circuit according toembodiments of the present invention.

FIG. 6A are territory maps representing four major arteries according toembodiments of the present invention.

FIG. 6B shows corresponding CBF maps for FIG. 6A according toembodiments of the present invention.

FIG. 6C are corresponding CBF weighted territory maps for FIG. 6Aaccording to embodiments of the present invention.

FIG. 7A are segmented and normalized gray matter maps at five locations.

FIG. 7B are territory maps of internal carotid and vertebral arteries(blue: right internal carotid, red: left internal carotid, green: rightvertebral, and yellow: left vertebral artery territories) according toembodiments of the present invention.

FIG. 7C are probabilistic territory maps of corresponding four majorarteries according to embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying figures, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Like numbers refer to like elementsthroughout. In the figures, certain layers, components or features maybe exaggerated for clarity, and broken lines illustrate optionalfeatures or operations unless specified otherwise. In addition, thesequence of operations (or steps) is not limited to the order presentedin the figures and/or claims unless specifically indicated otherwise. Inthe drawings, the thickness of lines, layers, features, componentsand/or regions may be exaggerated for clarity and broken linesillustrate optional features or operations, unless specified otherwise.Features described with respect to one figure or embodiment can beassociated with another embodiment of figure although not specificallydescribed or shown as such.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, steps, operations, elements, components, and/or groupsthereof. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that although the terms “first” and “second” areused herein to describe various actions, steps or components and shouldnot be limited by these terms. These terms are only used to distinguishone action, step or component from another action, step or component.Like numbers refer to like elements throughout.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andrelevant art and should not be interpreted in an idealized or overlyformal sense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

The term “circuit” refers to an entirely software embodiment or anembodiment combining software and hardware aspects, features and/orcomponents (including, for example, a processor and software associatedtherewith embedded therein and/or executable by, for programmaticallydirecting and/or performing certain described actions or method steps).

The term “programmatically” means that the operation or step can bedirected and/or carried out by a digital signal processor and/orcomputer program code. Similarly, the term “electronically” means thatthe step or operation can be carried out in an automated manner usingelectronic components rather than manually or using any mental steps.

The terms “MRI scanner” or MR scanner” are used interchangeably to referto a Magnetic Resonance Imaging system and includes the high-fieldmagnet and the operating components, e.g., the RF amplifier, gradientamplifiers and processors that typically direct the pulse sequences andselect the scan planes. Examples of current commercial scanners include:GE Healthcare: Signa 1.5T/3.0T; Philips Medical Systems: Achieva1.5T/3.0T; Integra 1.5T; Siemens: MAGNETOM Avanto; MAGNETOM Espree;MAGNETOM Symphony; MAGNETOM Trio; MAGNETOM Verio; and SKYRA scanner. Asis well known, the MR scanner can include a main operating/controlsystem that is housed in one or more cabinets that reside in an MRcontrol room while the MRI magnet resides in the MR scan room. Thecontrol room and scan room can be referred to as an MR suite and the tworooms can be separated by an RF shield wall. The term “high-magneticfield” refers to field strengths above about 0.5 T, typically above1.0T, and more typically between about 1.5T and 10T. Embodiments of theinvention may be particularly suitable for 1.5T, 2.0T and 3.0T systems,or higher field systems such as future contemplated systems at 4.0T,5.0T, 6.0T and the like. The methods and systems can also be applied toanimal MRI data acquired from animal MRI scanners. The term “patient”refers to humans and animals.

The term “automatically” and derivatives thereof means that theoperation and/or method can be substantially, and typically entirely,carried out without manual input, and is typically programmaticallydirected and/or carried out. The term “electronically” with respect toconnections includes both wireless and wired connections betweencomponents.

The term “clinician” means physician, neurologist, radiologist,physicist, or other medical personnel desiring to review medical data ofa patient. The term “workstation” refers to a display and/or computerassociated with a clinician.

The term “reconstruction” is used broadly to refer to original orpost-acquisition and storage and subsequent construction of image slicesor images of an image data set.

Each article, reference and patent cited or discussed herein is herebyincorporated by reference as if recited in full herein.

Embodiments of the invention are particularly suitable for evaluatingMRI image data but can also be useful for post-acquisition analysis ofimage data from other imaging modalities, including CT (computedtomography) and PET (Positron Emission Tomography), for example.

The term “color-coded” (or color-encoded) refer to a defined uniquecolor or color scale of pixels/voxels correlated to source arterylocation and/or blood flow direction to illustrate vessel (e.g., sourceartery) and blood flow direction.

The color map(s) can have both x- and y-directional modulation so that auser can visually ascertain which source artery and/or direction thesource artery is located for particular perfusion regions. The colormap(s) can indicate the associated feeding artery per voxel in uniquecolors. For example, right internal carotid artery may be displayed inblue, left internal carotid artery in red, and right vertebral artery incyan, and left vertebral artery in yellow. Thus, for example, inx-direction modulation, a first color, such as blue, represents that thesource artery is to the right while a second color, such as red,indicates that the source artery is to the left. One color, e.g., red,can refer to “from anterior” and another color, e.g., yellow, can referto “from posterior” in y directional modulation. The color-coded map canalso be configured to illustrate an amount of perfusion by a scale ofbrightness such that brightness indicates intensity of each voxel thatis proportional to blood flow for a respective voxel. Also, to complywith patent filing rules, black and white copies or grey scale versionsof these images may be used in support of the application.

The term “about” refers to a parameter that can vary from the recitedvalue, typically between +/−20%. For time parameters in minutes orhours, for example, the stated value includes times that are +/−5minutes of that number.

The term “time of flight” (TOF) refers to MRI angiography that is basedon the phenomenon of flow-related enhancement of spins entering into animaging slice. As a result of being unsaturated, these spins can producemore signal that surrounding stationary spins.

PCASL-based VE-ASL methods often require long scan times and complicatedclustering algorithms to classify multiple vascular territories.Embodiments of the invention can be used as an analysis tool or modulewith systems that are configured to perform VE-ASL.

The term “label space” refers to the 2-D space in the neck of a patientwhere blood signal is labeled when it passes a respective defined plane.

The term “cluster” or “clustering” refers to a set of contiguous orneighboring voxels of image data that have at least one substantiallysimilar (e.g., the same) value image parameter. Typically, the imageparameter is source location in Cartesian coordinates (e.g., a clusterof neighboring voxels having an intensity at the same x, y position orwithin 1 unit of position in either an x- or y- or x- and y-direction).For example, voxels sharing at least one common edge can be consideredas neighbors (the 18 connectivity scheme for a 3-D image).

For example, for a 3×3×3 voxel cube in a 3-D space, all the voxelsincluding or except eight corner voxels are considered to be connectedto the voxel at the center.

The term “territory” and derivatives thereof refer to renderings of (2-Dor 3-D) vascular maps with related vascular sources or related potentialvascular sources identified in like color. The term “clusteredterritory” means a 2-D or 3-D territory that has at least one common x,y source vessel location based on electronically identified clusters oflike voxels.

The terms “weighted CBF territory map” and “CBF weighted territory map”are used interchangeably and mean that proportions of blood flowindicated in the map are scaled to reflect qualitative or quantitativemeasures of blood flow, preferably quantitative measures of blood flow.

Generally stated, embodiments of the invention provide automatedvascular territory segmentation algorithms using connectivityinformation from both image space and label space. The territorysegmentation algorithms have two assumptions: (1) a territory may havemultiple source locations depending on the detection resolution, vesseldiameter, and vessel turns in the label plane but the multiple locationsmust be neighboring; and (2) a single artery may supply multiplenon-contiguous areas because of branching after leaving the labelingplane.

FIG. 1 illustrates an example of a sequence of analysis steps that canbe used to provide an automated (electronic) vascular territorysegmentation to segment an image volume into separate vascularterritories. FIG. 1 illustrates steps of a segmentation algorithm ormodule that uses source location in (x, y) coordinates of a coordinatesystem. The coordinate system is typically a Cartesian coordinatesystem.

First (shown as Step 1), three dimensional (3-D) connectivity can beapplied to source image data to identify clustering with a small clustersize in image space on a voxel-wise basis to generate clusteredterritories. Each clustered territory has a same source location in (x,y) coordinates. The clustering can identify small clusters of contiguousor neighboring voxels of at least about 4-6 voxels that have the samesource location. The small cluster size can include clusters of at least4-6 neighboring voxels, typically 4 or more neighboring voxels. Smallerclusters, with a smaller cluster size less than 4 neighboring voxels,can be used as a threshold to reject associated voxels as beingcontaminated by noise. The 3-D connectivity can be carried out simplyusing physical contiguity. For example, the voxels having connectivityare voxels that are physically in contact in the image space. The sourceimage data can include any medical image data set. In some embodiments,the source image data comprises MRI image data of a patient's brain withsource locations in A/P and R/L directions.

Next (shown as Step 2 in FIG. 1), the source locations of territoriesfrom Step 1 are mapped in 2-D label space and the sources are clusteredbased on spatial connectivity. The 2-D clustering can be carried outagain based simply on physical contiguity and/or based on a statisticaldistribution. In particular embodiments, the 2-D clustering analysisthat establishes source locations is based on physical contact. This isapplied based on assumption 1 noted above.

As shown in Step 3, territories corresponding to the source clustersfrom Step 2 are generated. Multiple 3-D spatial clusters may stem from asingle source based on assumption 2.

Next, as shown in Step 4, from each territory identified in Step 3, thecenter of mass (e.g., the centroid) to label space is calculated andtested to determine if multiple territories are from a same source.Clusters are regarded from the same source if the calculated distancesbetween cluster centroids is smaller than a detection resolution definedin the source image data. For example, the case shown in FIG. 1 has thedetection resolutions of 3 mm in A/P (or in y-direction) and 9 mm in R/L(or in x-direction). The clustered source(s) in Step 2 may now beseparated into multiple sources if the distances between clustercentroids are larger than the detection resolution. The separation mayindicate that the multiple sources were clustered in Step 2 due toproximity but they act as independent sources. As shown for Step 5, athresholding and vascular connectivity test can be carried out forfurther resolving source location using the centroid calculations andsources can be numbered and presented in color coding. The analysis canidentify a reduced number of territories relative to the thresholdingand vascular connectivity test. Small territories (e.g., about 30 voxelsor less) can be rejected as not containing sufficient vascular sourceinformation and hence are not used to create a CBF territory map.

Optionally, source locations of surviving territories can be validatedat this stage using a high resolution MR angiogram with a region growingalgorithm obtained at the label plane to determine if multiple sourcesare from the same artery. The “validation” may be particularlyappropriate where a single artery generates two source locations in aterritory due to a lateral turn in labeling space.

As shown in FIG. 1, the CBF map and MRA (if provided) can be used togenerate a CBF color territory map and a separate source estimation mapwith sources identified in color and number. The source estimation mapnumbers can be ordered based on cluster size, from smallest to largest(or the reverse).

The above analysis protocol/ algorithm was tested using data obtainedwith Fourier encoded ASL (2) in the A/P direction and with a phaseoffset in the R/L direction. The detection resolution was 3 mm in A/Pand 9 mm in R/L. A maximum intensity projection (MIP) image from atime-of-flight angiogram (1 cm thickness) was used to overlay estimatesof source locations and determine if multiple sources are from a singleartery moving laterally within the labeling space.

FIGS. 2A-2E show results from placement of the labeling plane at twolocations: a superior location where multiple branches of the middlecerebral artery supply cortical gyri (blue in FIG. 2A), and a moreinferior location 2 cm above the circle of Willis (red in FIG. 2B). Theproposed algorithm segmented the images into 19 (FIG. 2B) and 12perfusion territories (FIG. 2C), respectively. There was one territoryin which two sources were actually from a single artery due to lateralturn in the labeling space. Small branches from thalamo-perforators tothe thalamus (orange and blue, source 9 and 10, FIG. 2C) andlenticulostriates to the basal ganglia (green, sources 11 and 7, FIG.2C) are identified. The algorithm was able to resolve separateterritories even with the neighboring sources (purple and blue, sources10 and 19, FIG. 2B).

FIG. 2A shows the label plane locations “upper” and “lower.” FIG. 2B and2-D show the estimated source locations overlaid on MIP images of therespective label location and FIGS. 2C and 2E show corresponding CBFweighted territory maps from the upper (FIG. 2C) and the lower (FIG.2-D) labeling locations. Numbering was ordered based on cluster size.

Because the analysis method/circuit or program uses mutual connectivityin both image and label space, the capability of segmenting twoneighboring territories can be limited when they are clustered in Step 2and 3. As noted above, a high detection resolution may be used toconfirm a separation in this situation. Verification of the vascularconnectivity in Step 5 may also or alternatively use manual editing.However, the analysis may potentially be totally automated through theuse of a high resolution MRA and a region growing algorithm.

FIG. 3 is a flow chart of exemplary operations that can be used to carryout embodiments of the present invention. The operations can beimplemented using a computer program product and/or at least oneprocessor to provide an automated vascular segmentation algorithm basedon vascular territory mapping. At least one source brain image can beprovided from a medical image data set (block 150). A three-dimensionalconnectivity clustering analysis is electronically applied to the brainimage data in image space on a voxel-wise basis to identify locations ofsmall clusters of voxels having at least one similar image parameter(e.g., intensity) to identify a potential x, y source vessel location(block 155). A first quantity of clustered territories electronicallygenerating based on the three-dimensional connectivity clusteringanalysis, each clustered territory having at least one associated sourcelocation in x, y coordinates (block 160). Then, source locations of theclustered territories in 2-D label space are electronically mapped withsource locations clustered based on spatial connectivity (block 165). Arespective clustered territory may have multiple neighboring sourcelocations depending on detection resolution, vessel diameter, and vesselturns in a respective label plane. A second quantity of clusteredterritories can be electronically generated based on the mapped sourcelocations (block 170). The second quantity of clustered territories canbe less than the first quantity of clustered territories. Multiplethree-dimensional spatial clusters may be associated with a singlesource. Then, a center of mass and/or centroid distance to label spaceis calculated for each of the second quantity of clustered territories(block 175). Then, a determination of whether multiple territories areassociated with a single source is performed. Different clusteredterritories are identified as belonging to a single source if thecalculated distance between centroids is smaller than a detectionresolution (block 180).

Optionally, a color-coded weighted cerebral blood flow (CBF) territorymap can be electronically generated, as may a source location estimationmap with source locations in color and a numbered order associated withcluster size.

The MRI signal acquistion can be carried out without requiring the useof an administered contrast agent. The vascular color-coded tissue mapcan be used to identify functional changes in vascular distributions, aswell as quantitative measures of blood flow per voxel. This informationcan be useful for individualized surgical planning and may be morepredictive of a resultant stroke than velocity information fromultrasound or measures of ICA luminal diameter.

Embodiments of the present invention may take the form of an entirelysoftware embodiment or an embodiment combining software and hardwareaspects, all generally referred to herein as a “circuit” or “module.”Furthermore, the present invention may take the form of a computerprogram product on a computer-usable storage medium havingcomputer-usable program code embodied in the medium. Any suitablecomputer readable medium may be utilized including hard disks, CD-ROMs,optical storage devices, a transmission media such as those supportingthe Internet or an intranet, or magnetic storage devices. Some circuits,modules or routines may be written in assembly language or evenmicro-code to enhance performance and/or memory usage. It will befurther appreciated that the functionality of any or all of the programmodules may also be implemented using discrete hardware components, oneor more application specific integrated circuits (asics), or aprogrammed digital signal processor or microcontroller. Embodiments ofthe present invention are not limited to a particular programminglanguage.

Computer program code for carrying out operations of the presentinvention may be written in an object oriented programming language suchas Java®, Smalltalk or C++. However, the computer program code forcarrying out operations of the present invention may also be written inconventional procedural programming languages, such as the “C”programming language. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on anothercomputer, local and/or remote or entirely on the other local or remotecomputer. In the latter scenario, the other local or remote computer maybe connected to the user's computer through a local area network (LAN)or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

Embodiments of the present invention are described herein, in part, withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems) and computer program products according toembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing some or all of thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowcharts and block diagrams of certain of the figures hereinillustrate exemplary architecture, functionality, and operation ofpossible implementations of embodiments of the present invention. Inthis regard, each block in the flow charts or block diagrams representsa module, segment, or portion of code, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that in some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the figures. For example, two blocks shown in successionmay in fact be executed substantially concurrently or the blocks maysometimes be executed in the reverse order or two or more blocks may becombined, or a block divided and performed separately, depending uponthe functionality involved.

FIGS. 4A-4C illustrate exemplary image processing systems 10 with aVascular Territory Segmentation circuit 200 and/or color coded brainvascular territory map module 201. The systems can be configured toautomatically generate color vascular territory maps using rapid (e.g.,under 5 minutes of active scanning) brain scans without requiring manualinput for identification of arteries to carry out the image processing.The workstation and/or Scanner can each include at least one processor60P, 75P, respectively, that can be configured to carry out all or partof the image analysis and image acquisition. The image analysis can beperformed post-acquisition in a device separate from the Scanner used toacquire the image data.

FIG. 4A illustrates that the system 10 can include at least oneworkstation 60 that has an optional computer portal for accessing themodule 201 and/or circuit 200. The module 201 can be held on a remoteserver accessible via a LAN, WAN, SAN or Internet. The workstation 60can communicate with patient image data which may be held in a remote orlocal server, in the Scanner 75 or other electronically accessibledatabase or repository. The workstation 60 can include a display with aGUI (graphic user input) and the access portal. The workstation canaccess the data sets via a relatively broadband high speed connectionusing, for example, a LAN or may be remote and/or may have lesserbandwidth and/or speed, and for example, may access the data sets via aWAN and/or the Internet. Firewalls may be provided as appropriate forsecurity.

FIG. 4B illustrates that the circuit 200 and module 201 can be includedin the MR Scanner 75 which can communicate with a workstation 60. Themodule 201 and/or circuit 200 can be integrated into the control cabinetof the MR Scanner with image processing or scan sequence controlcircuitry. FIG. 4C illustrates that the circuit 200 and/or module 201can be integrated into one or more local or remote workstations 60 thatcommunicates with the Scanner 75. Although not shown, parts of thecircuit or module can be held on both the Scanner 75 and one or moreworkstations 60, which can be remote or local. The module and circuitcan be combined or separated into further components.

The circuits and modules 200, 201 and methods of embodiments of theapplication can provide vascular territory mapping using non-contrastenhanced (NCE-) MRA methods.

Embodiments of the invention can be used clinically for variousconditions including screening and analysis of impairments, disease andthe like including, but not limited to, carotid artery stenosis. For thelatter, it is expected that the degree of carotid stenosis can beidentified based on a quantified collateral flow from the vascularterritory mapping methods described herein.

The methods are also capable of resolving multiple sources feeding bloodto a single voxel.

FIG. 5 is a schematic illustration of a circuit or data processingsystem 290. The system 290 can be used with any of the systems 10 andprovide all or part of the circuit 200 and/or module 201. The circuitsand/or data processing systems 290 data processing systems may beincorporated in a digital signal processor in any suitable device ordevices. As shown in FIG. 5, the processor 410 can communicate with anMRI scanner 75 and/or workstation 60 with memory 414 via an address/databus 448. The processor 410 can be any commercially available or custommicroprocessor. The memory 414 is representative of the overallhierarchy of memory devices containing the software and data used toimplement the functionality of the data processing system. The memory414 can include, but is not limited to, the following types of devices:cache, ROM, PROM, EPROM, EEPROM, flash memory, SRAM, and DRAM.

FIG. 5 illustrates that the memory 414 may include several categories ofsoftware and data used in the data processing system: the operatingsystem 452; the application programs 454; the input/output (I/O) devicedrivers 458; and data 455. The data 455 can include patient-specific MRIimage (slice) data. FIG. 5 also illustrates the application programs 454can include (an image reconstruction) Vascular segmentation Module 450and a weighted CPF territory map Module 451 (with or without the colorcoded or color encoded source estimation map). Optionally, theapplication programs can also include a Fourier encoded ASL module thatcan cooperate with the Segmentation Module to generate color codedand/or encoded vascular maps of the brain. See, e.g., U.S. patentapplication Ser. No. 13/780,323, filed Feb. 28, 2013, entitled, VesselEncoded Aterial Spin Labeling Using Fourier Encoding Suitable ForVascular Territory Mapping, the contents of which are herebyincorporated by reference as if recited in full herein.

As will be appreciated by those of skill in the art, the operatingsystems 452 may be any operating system suitable for use with a dataprocessing system, such as OS/2, AIX, DOS, OS/390 or System390 fromInternational Business Machines Corporation, Armonk, NY, Windows CE,Windows NT, Windows95, Windows98, Windows2000, windowsxp or otherWindows versions from Microsoft Corporation, Redmond, Wash., Unix orLinux or freebsd, Palm OS from Palm, Inc., Mac OS from Apple Computer,labview, or proprietary operating systems. The I/O device drivers 458typically include software routines accessed through the operatingsystem 452 by the application programs 454 to communicate with devicessuch as I/O data port(s), data storage 455 and certain memory 414components. The application programs 454 are illustrative of theprograms that implement the various features of the data (image)processing system and can include at least one application, whichsupports operations according to embodiments of the present invention.Finally, the data 455 represents the static and dynamic data used by theapplication programs 454, the operating system 452, the I/O devicedrivers 458, and other software programs that may reside in the memory414.

While the present invention is illustrated, for example, with referenceto the Module 450 being an application program in FIG. 5, as will beappreciated by those of skill in the art, other configurations may alsobe utilized while still benefiting from the teachings of the presentinvention. For example, the Module 450 may also be incorporated into theoperating system 452, the I/O device drivers 458 or other such logicaldivision of the data processing system. Thus, the present inventionshould not be construed as limited to the configuration of FIG. 5 whichis intended to encompass any configuration capable of carrying out theoperations described herein. Further, Module 450 can communicate with orbe incorporated totally or partially in other components, such as an MRIscanner 75, interface/gateway or workstation 60.

The I/O data port can be used to transfer information between the dataprocessing system, the workstation, the MRI scanner, theinterface/gateway and another computer system or a network (e.g., theInternet) or to other devices or circuits controlled by the processor.These components may be conventional components such as those used inmany conventional data processing systems, which may be configured inaccordance with the present invention to operate as described herein.

FIGS. 6A-6C show an example of the invention when the tagging plane tobe spatially encoded was located below the confluence to the basilarartery so as to encode internal carotid and vertebral arteries. FIG. 6Ashows territory maps of internal carotid and vertebral arteries (blue:right internal carotid, red: left internal carotid, cyan: rightvertebral, and yellow: left vertebral artery territories). FIG. 6B arecorresponding CBF maps and FIG. 6C are CBF weighted territory mapsindicating the source location and the amount of blood flow in a voxel.

The segmentation analysis contemplated by embodiments of the inventioncan be used with reconstruction of various medical image data setswhether “raw” or pre-processed using various processing methods such as,but not limited to that proposed by Wong et al, US 2012/0271157 A1,Mapping Vascular Perfusion Territories Using Magnetic Resonance Imaging,the content of which is hereby incorporated by reference as if recitedin full herein. Stated differently, output from this other analysis canbe used as input for the segmentation analysistools/methods/programs/modules/algorithms described herein.

Embodiments of the invention provide a novel vascular territory mappingmethod requiring minimal operator intervention and simplepost-processing routines that are suitable for clinical implementation.In addition, the methods can provide voxel-wise quantitative mapping ofblood flow in the brain. The invention will be explained further by wayof the non-limiting Examples below.

EXAMPLES Probabilistic Cerebral Vascular Territory Atlases

Physiologically accurate mapping of cerebral blood flow in multipleseparate vascular territories has a wide range of potential research andclinical applications, including the investigation and diagnosis ofnumerous common disease conditions that affect cerebral perfusion, suchas migraine, carotid stenosis, and extracranialintracranial bypassbefore and after surgery. The identification of functional changes invascular distributions, as well as quantitative measures of blood flowper voxel may be useful for individualized surgical planning, such aspredicting the risk of potential iatrogenic ischemic stroke. Moreover,anatomical variations of the cerebral arteries and knowledge of thisvariation can avoid misdiagnosis. Probabilistic vascular territoryatlases are well suited to take this vascular variation into account.Therefore, access to detailed vascular territory atlases may serve toadvance understanding of the pathophysiology of diseases and the effectsof interventions and treatments. To date, however, it is believed thatonly crude cerebral vascular territory atlases exist based ondigitization of colorized figures, without any atlas generated by directmeasurement of cerebral blood flow.

Methods

Data was obtained from 20 normal patients (4 male and 16 female, agerange: 2-41 yrs.), with no evidence of disease or vascular abnormalityThe data was collected on a 3T Siemens SKYRA scanner with a 20 channelhead/neck coil (Siemens AG, Erlangen, Germany). Vascular territory mapswere obtained with a Fourier encoded ASL scan [Jung, 20th ISMRM: 581,2012] using 2D EPI acquisition. Imaging parameters include 1.6 s taggingduration, 1.2s post-labeling delays, 22 ms/4 s TE/TR, 3.75 mm×3.75 mmin-plane resolution, 5 mm slice thickness, 24 axial slices. Fourierencoding parameters were: 9 cm×6.6 cm encoding FOV, 15×11 encoding steps(7×5 skipped steps), 6×6 mm encoding resolution, 56 repetitions, and 4min scan time. The tagging plane to be spatially encoded was locatedbelow the confluence to the basilar artery so as to encode internalcarotid and vertebral arteries. A high-resolution T1-weighted scan wasalso obtained for all subjects using a MP-RAGE sequence.

Source locations of the primary component from Fourier encoded ASL in xand y axis were processed using a territory segmentation algorithm [Junget al., 21th ISMRM: 2154, 2013], which utilizes mutual connectivityinformation from both image and label spaces. The content of the Jung etal. references noted in the Examples section are hereby incorporated byreference as if recited in full herein.

The segments of four major arteries were categorized into two internalcarotid and two vertebral arteries based on the relative position in thetagging plane. Each segment was confirmed by visual inspection of thelocation.

FIGS. 7A-7C illustrate images generated from the collected data. FIG. 7Aare segmented and normalized gray matter maps at five locations. FIG. 7Bare territory maps of internal carotid and vertebral arteries (blue:right internal carotid, red: left internal carotid, green: rightvertebral, and yellow: left vertebral artery territories) according toembodiments of the present invention. FIG. 7C are probabilisticterritory maps of corresponding four major arteries according toembodiments of the present invention.

T1-weighted images were processed for tissue segmentation and spatialbrain normalization to the Montreal Neurological Institute (MNI) braintemplate using SPM8. The territory maps were coregistered to thestructural T1 and normalized to MNI space using the transformationcomputed above. Per voxel basis probabilistic territory maps shown inFIG. 7C were computed by taking a ratio of the number of subjects havinga certain source artery to the total number of subjects having anysource artery. Vascular territory maps shown in FIG. 7B were generatedby choosing the source artery having highest probability in a voxel.

Results

The vascular territory maps indicate that the internal carotid arteriessupply blood to anterior and middle cerebral artery regions while thevertebral arteries primarily supply to posterior cerebral artery region.However, the probabilistic territory maps from individual feedingarteries represent the subject variability, which may not be shown withconventional vascular territory maps. Two interesting findings wereobserved: 1) 15% to 20% of subjects show blood supply to the right ACAregion from contra-lateral flow of left ICA via the anteriorcommunicating artery, but not vice versa, and 2) there is supply fromthe internal carotid arteries to the PCA region via the posteriorcommunicating arteries, but no flow from PCA through posteriorcommunicating arteries to supply ACA or MCA territories.

Discussions

These methods provide a frame-work for generating detailed vascularterritory atlases that may have utility as clinical diagnostic and basicresearch tools. The acquisition of more data for normal subjects andthose with diseases secondary to cerebral vascular; however, will beuseful to determine the true utility as a clinical and research tool.With a larger sample size, gender-related and other group phenotypicvariations may be explored. In addition, even though the cerebralvasculature is typically mature at birth, potential age-relatedvariation may be of interest.

CONCLUSION

Thus, experiment-based vascular territory atlases of major arteries,which quantitatively map downstream cerebral perfusion may haveimportant utility as a clinical diagnostic and basic research tool.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe claims. In the claims, means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not only structural equivalents but also equivalent structures.Therefore, it is to be understood that the foregoing is illustrative ofthe present invention and is not to be construed as limited to thespecific embodiments disclosed, and that modifications to the disclosedembodiments, as well as other embodiments, are intended to be includedwithin the scope of the appended claims. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

That which is claimed:
 1. An automated vascular territory segmentationmethod to identify arterial source location, comprising: providing atleast one source image data set of a brain of a subject; electronicallyapplying a three-dimensional connectivity clustering analysis to thebrain image in image space on a voxel-wise basis to identify locationsof small clusters of voxels having at least one image parameter that issubstantially the same to identify a potential x, y source vessellocation; electronically generating a first quantity of clusteredterritories based on the electronically applying step, each clusteredterritory having at least one associated source location in x, ycoordinates; then electronically mapping source locations of theclustered territories in 2-D label space with source locations clusteredbased on spatial connectivity, wherein a respective clustered territorymay have multiple neighboring source locations depending on detectionresolution, vessel diameter, and vessel turns in a respective labelplane; electronically generating a second quantity of clusteredterritories based on the mapped source locations, wherein the secondquantity of clustered territories is less than the first quantity ofclustered territories, and wherein multiple three-dimensional spatialclusters may be associated with a single source; then calculating acentroid distance to label space for each of the second quantity ofclustered territories; then electronically determining if multipleterritories are associated with a single source to evaluate vascularconnectivity, wherein different clustered territories are identified asbelonging to a single source if an associated calculated centroiddistance is smaller than a detection resolution; then electronicallygenerating at least one color-coded cerebral blood flow (CBF) territorymap using source locations based on the vascular connectivity.